I present the results of an articulatory (EMA and aerodynamic) and acoustic study of the realizations of three oral and nasal vowel pairs /a/-/˜ɑ/, /ɛ/-/˜ɛ/, and /o/-/˜ɔ/ recorded from 11 Northern Metropolitan French (NMF) and two Quebecois French (QF) female speakers in laboratory settings. Using simultaneous acoustic and articulatory information related to the lingual and labial articulations, I investigated how the oral/nasal vowel distinction is manifested with regard to differences in lingual and labial articulatory configuration, for each of these vowel pairs and in both of these respective dialects. Based on previous research, I expected to find evidence that all nasal vowels are produced with at least some change in lingual and labial articulatory configuration compared to their oral vowel counterparts in both dialects. By studying the position and movement of the tongue and lips during the production of target oral and nasal vowels and simultaneously recording the acoustic signal, I was able to separate the effects of velo-pharyngeal coupling and oral articulatory configuration on the acoustic output of the vocal tract. I find that in both dialects, all three nasal vowels are produced with some degree of modification of the oral articulators in comparison with their oral counterparts.
With regard to the NMF dialect: for [ɛ]-[˜ɛ], in addition to velo-pharyngeal coupling, the acoustic distinction was most likely due to changes in tongue body position, with the tongue lowered and more retracted for [˜ɛ] than for [ɛ]. For [a]-[˜ɑ], in addition to velo-pharyngeal coupling, the acoustic distinction was most likely due to a combination of lingual and labial articulations, with consistent labial articulatory differences between the two vowels, as /˜ɑ/ was produced with more lip rounding and/or protrusion than /a/ across speakers. For [o]-[˜ɔ], much inter-speaker articulatory variability, but relatively little inter-speaker acoustic variability, was observed. In general, the speakers use either primarily lingual position, or a combination of lingual position and lip rounding and/or protrusion to maintain oral articulatory differences between [o] and [˜ɔ]. The articulatory and acoustic analyses suggest that, in addition to velo-pharyngeal opening, NMF speakers may employ a combination of lingual, labial, and/or passive oral articulations (i.e., "velic" constriction due to lowering the velum) in order to reach the acoustic target for [˜ɔ]. Furthermore, patterns of F1 are somewhat contradictory, as an equal N of speakers show either no difference or higher F1 for [˜ɔ]. However, the most common pattern is a lower F1 for [˜ɔ] compared to [o] (seven of 11 speakers). Similarly, nine of 11 speakers' renditions of the target words indicate a lower F2 for [˜ɔ] compared to [o]. I found evidence of a counter-clockwise chain shift in the realizations of the three nasal vowels. However, I found evidence that the oral articulatory contributions to this chain shift are different for the three vowels: for [˜ɛ], it is due primarily to a lower, retracted tongue position; for [˜ɑ] it is due primarily to tongue retraction and lip rounding; and for [˜ɔ], it is due primarily to a speaker-specific combination of tongue retraction and/or lip rounding. With regard to the QF dialect, I observed a lingual diphthong production of [˜ɛ] and a labial diphthong production of [˜ɔ], and I found evidence pointing to the existence of a nasal coda in the realization of [˜ɛ]. I did not find strong indications of a clockwise chain shift in the realizations of the three nasal vowels as produced by the two QF speakers in this study.
Inter-speaker variation in oral articulation and the dispersion of the NMF vowels in the acoustic space suggests variable but acoustically equivalent speaker strategies in the production of nasal vowels in NMF that I propose to interpret in terms of motor equivalence. Specifically, the results suggest that a similar acoustic dispersion is maintained across speakers within a given dialect, although speakers may use different lingual and labial configurations---in conjunction with velo-pharyngeal coupling---in order to achieve a particular acoustic goal. This inter-speaker variation may help explain partially contradictory findings observed across previous studies: various studies have observed different results with regard to tongue position for [˜ɑ] compared to [a] and for [˜ɔ] compared to [o]; I propose that these differences are due to inter-speaker variation with regard to how these nasal vowels are articulated, rather than due to differences in methodology between these studies. An important finding from the articulatory results of this study is that, in general, the oral articulatory differences for the nasal vowels in NMF compared to their oral counterparts are predicted to result in modifications to the frequencies of both F1 and F2 which are also predicted to result from velo-pharyngeal coupling (i.e., centralization of the vowel space along the F1 dimension and lowering of F2 for non-back vowels). In light of these results, I propose that the oral articulations of the nasal vowels in NMF might have evolved over time to enhance and reinforce the formant-frequency-related acoustic effects of nasalization. Although I do not observe this same pattern for the realizations of the nasal vowels in QF, I suggest that dynamic oral articulations and nasal coda production contribute to the distinctive nasality of the nasal vowels in the dialect instead. Moreover, with regard to NMF, I posit that the F1-lowering due to velo-pharyngeal coupling was likely a catalyst for the onset of a push chain shift in the realization of the nasal vowels, a nasal vowel shift that should be regarded as a continually evolving phenomenon, given the realizations observed in this study. Specifically, I observe that /˜ɛ/ is realized as [˜5], that /˜ɑ/ is realized as [˜(lowered)ɔ], and that /˜ɔ/ is realized as [˜(raised)o]. Given the discrepancies between the traditional IPA transcriptions used for these three vowels and the realizations observed here, I offer the transcriptions [˜5]-[˜(lowered)ɔ]-[˜(raised)o] as possible revisions to the IPA transcriptions used for the respective nasal vowels in NMF.